[PATCH] ARM: add boot image dependencies not to generate invalid images

[Masahiro Yamada]

Hi Russel,

No more comment?
I answered your question.




2015-07-11 1:41 GMT+09:00 Masahiro Yamada <yamada.masahiro at socionext.com>:
> Hi Russel,
>
>
> 2015-07-10 19:22 GMT+09:00 Russell King - ARM Linux <linux at arm.linux.org.uk>:
>> On Mon, Jul 06, 2015 at 09:37:04PM +0900, Masahiro Yamada wrote:
>>> [3] Then, re-build "all" and "uImage" simultaneously.
>>>     You will get an invalid uImage at random.
>>>   $ make -s -j8 ARCH=arm UIMAGE_LOADADDR=0x80208000 all uImage
>>>   Image Name:   Linux-4.2.0-rc1-00008-g1c4c715-d
>>>   Created:      Mon Jul  6 17:52:22 2015
>>>   Image Type:   ARM Linux Kernel Image (uncompressed)
>>>   Data Size:    26768 Bytes = 26.14 kB = 0.03 MB
>>>   Load Address: 80208000
>>>   Entry Point:  80208000
>>
>> At no point in the above do I see an attempt to rebuild init/main.o,
>> which there should be as you touched the corresponding .c file -
>> because you're hiding that output with -s.  Please show what's going
>> on without using -s.
>
> Please see the log attached at the end of this message.
>
>
>>> "make uImage" could descend into arch/arm/boot/Makefile before
>>> "make zImage" is completed because arch/arm/Makefile describes no
>>> dependency among boot targets.
>>
>> The uImage target should depend on vmlinux, which should force the
>> rebuild of init/main.o, and relink of the top-level vmlinux file
>> before decending into arch/arm/boot/Makefile for the
>> arch/arm/boot/uImage target.
>>
>> That makefile contains the dependencies required to order things
>> correctly - the arch/arm/boot/uImage target depends on
>> arch/arm/boot/zImage, which in turn depends on
>> arch/arm/boot/compressed/vmlinux, and then arch/arm/boot/Image.
>>
>> In other words, arch/arm/boot/Makefile deals with the dependencies
>> between the targets it's responsible for building itself.
>
> No, you do not understand what is happening in here.
>
>
> The dependencies among targets such as Image, zImage, uImage,
> are fully described in arch/arm/boot/Makefile, but it is not enough.
>
> Because arch/arm/boot/Makefile is _not_ included from the top-level Makefile,
> the top-level build cannot know the dependency between zImage and uImage.
>
> arch/arm/Makefile, which is included from the top Makefile,
> only describes that zImage depends on vmlinux,
> and uImage depends on vmlinux as well.
> But, no dependency between zImage and uImage is written in arch/arm/Makefile.
>
> Consequently, we run make with the parallel option, first Kbuild
> updates vmlinux,
> and then two different threads descends into arch/arm/boot/Makefile
> almost at the same time, one for updating zImage and the other for uImage.
>
> The is a race between the two threads.
>
> While one thread is re-generating zImage and also uImage on top of that,
> the other thread tries to re-generate zImage independently.
>
> zImage is overwritten by the slower thread, and then uImage is
> re-generated based on the broken zImage.
>
> See my detailed build log below:
>
> Please note:
> "Kernel: arch/arm/boot/zImage is ready"
> is displayed twice,
> the first one is shown before the uImage log, and the second one is
> after uImage.
>
> zImage is correct, but uImage is extremely small when this problem happens.
>
>
>
> $ git describe
> v4.2-rc1-62-gc4b5fd3
>
>
> $ touch init/main.c
> $ make -j8 ARCH=arm UIMAGE_LOADADDR=0x80208000 all uImage
>   CHK     include/config/kernel.release
>   CHK     include/generated/uapi/linux/version.h
>   CHK     include/generated/utsrelease.h
> make[1]: `include/generated/mach-types.h' is up to date.
>   CHK     include/generated/timeconst.h
>   CHK     include/generated/bounds.h
>   CHK     include/generated/asm-offsets.h
>   CALL    scripts/checksyscalls.sh
>   CC      init/main.o
>   CHK     include/generated/compile.h
>   LD      init/built-in.o
>   LINK    vmlinux
>   LD      vmlinux.o
>   MODPOST vmlinux.o
>   GEN     .version
>   CHK     include/generated/compile.h
>   UPD     include/generated/compile.h
>   CC      init/version.o
>   LD      init/built-in.o
>   KSYM    .tmp_kallsyms1.o
>   KSYM    .tmp_kallsyms2.o
>   LD      vmlinux
>   SORTEX  vmlinux
>   SYSMAP  System.map
>   OBJCOPY arch/arm/boot/Image
>   Building modules, stage 2.
>   Kernel: arch/arm/boot/Image is ready
>   GZIP    arch/arm/boot/compressed/piggy.gzip
>   AS      arch/arm/boot/compressed/piggy.gzip.o
>   Kernel: arch/arm/boot/Image is ready
>   GZIP    arch/arm/boot/compressed/piggy.gzip
>   LD      arch/arm/boot/compressed/vmlinux
>   OBJCOPY arch/arm/boot/zImage
>   Kernel: arch/arm/boot/zImage is ready
>   UIMAGE  arch/arm/boot/uImage
> Image Name:   Linux-4.2.0-rc1-00062-gc4b5fd3-d
> Created:      Sat Jul 11 01:22:22 2015
> Image Type:   ARM Linux Kernel Image (uncompressed)
> Data Size:    26472 Bytes = 25.85 kB = 0.03 MB
> Load Address: 80208000
> Entry Point:  80208000
>   Image arch/arm/boot/uImage is ready
>   MODPOST 192 modules
>   AS      arch/arm/boot/compressed/piggy.gzip.o
>   LD      arch/arm/boot/compressed/vmlinux
>   OBJCOPY arch/arm/boot/zImage
>   Kernel: arch/arm/boot/zImage is ready
> $ LANG=C ls -l arch/arm/boot/
> total 19636
> -rwxrwxr-x 1 masahiro masahiro 13766656 Jul 11 01:22 Image
> -rw-rw-r-- 1 masahiro masahiro     3137 Jul  3 01:17 Makefile
> drwxrwxr-x 2 masahiro masahiro     4096 Jul  3 01:17 bootp
> drwxrwxr-x 2 masahiro masahiro     4096 Jul 11 01:22 compressed
> drwxrwxr-x 3 masahiro masahiro   155648 Jul 11 00:58 dts
> -rw-rw-r-- 1 masahiro masahiro     1648 Jul  3 01:17 install.sh
> -rw-rw-r-- 1 masahiro masahiro    26536 Jul 11 01:22 uImage
> -rwxrwxr-x 1 masahiro masahiro  6135048 Jul 11 01:22 zImage
>
>
>
>
>
>
>
> --
> Best Regards
> Masahiro Yamada



-- 
Best Regards
Masahiro Yamada